text: let myBirthTime = new Date(1998, 12 - 1, 9);
  function updateParagraph() {
    let now = new Date();
    let seconds = (now.getTime() - myBirthTime.getTime()) / 1000;
    document.getElementById("birth-time").innerText =
      "生まれてから" + seconds + "秒経過。";
  }
  
  setInterval(updateParagraph, 50);
  
  function areaOfCircle(hankei) {
    let menseki = hankei * hankei * 3.14;
    return menseki;
  }
  
  document.write(areaOfCircle(5));
  